Method for incorporating a drying oil in a fibrous composition and the improved product



United States Patent Ofifice $355,795 Patented Sept. 25, 1962 METHOD FOR INCORPORATING A DRYING OIL IN A HEROES COMPQSITION AND THE IM- PRUVED PRQDUCT Harland H. Young, Western Springs, and Jack R. Newman and Edward J. Majka, Chicago, Ill., assignors to Swift & Company, Chicago, Ill, a corporation of Illinois No Drawing. Filed Dec. 19, 1955, Ser. No. 553,682

8 Claims. (Cl. 162164) This invention relates to a new and improved method for incorporating a drying oil in a fibrous composition and to an improved oil-containing fibrous composition.

Historically, oil tempered boards have been manufactured by dipping the finished hardboard in a large tank of drying oil, leaving the hardboard for a short interval of time in the oil to permit absorption and thereafter baking the oil-soaked board in an oven at a temperature within the range of 300-400 F. for 3-6 hours in order to set the oil to a resin-like material. This conventional manner of manufacturing requires a monetary outlay for the installation and maintenance of the oil dipping equipment and frequently the tempering oil is not uniformly distributed throughout the board as there is a greater saturation of the board at the two surfaces than in the interior. Boards are tempered primarily to increase strength and in addition, the oil will impart some resistance to weather. In the manufacture of paper, oil is added to the fibrous composition in order to impart desirable characteristics, the chief reasons being to increase the wet strength of the paper and to decrease its susceptibility to moisture.

We have found that drying oil may be readily incorporated in a lignocellulosic fibrous material with more uniformity of dispersion, with less equipment, and with a saving in time over that required in conventional processing. In the proces of this invention, We propose to incorporate the drying oil in the fibrous composition by introducing it to the fiber in an aqueous solution of a water soluble salt of a Diels Alder condensation product, and precipitating the Diels-Adler condensation product on the fiber. In the manufacture of hardboard, the fibrous composition is thereafter heated to set the condensation product to a resin-like material. The Diels Alder reaction is discussed generally at pages 28788 in Textbook of Organic Chemistry, Fieser and Fieser, 1950, D. C. Heath and Company, Boston.

In carrying out our invention, a conventional drying oil, for example, tung, linseed, oiticica, dehydrated castor, soybean, safflower, and other oils having conjugated double bonds is reacted with an unsaturated carboxylic acid whose unsaturated function is conjugated with the carboxyl group. Examples of such acids are maleic, fumaric, citraconic, pyrocinchonic, di and tetra hydrophthalic, itaconic, and their anhydrides. Unsaturated carboxylic acids of this class undergo a condensation ,known as the Diels-Alder reaction with drying oils in which the ethylenic function of the conjugated system of the acid adds to and is bound by the conjugated system existing in the fatty acid chains of the oil. This condensation is brought about by merely warming the unsaturated carboxylic acid with the drying oil to a temperature Within the approximate range of 1202 C. so as to produce a polycarboxylated modified drying oil. Peroxide catalysts are helpful but not essential. The molal ratio of drying oil to the unsaturated carboxylic acid or its anhydride can vary over a wide range but we prefer to use a ratio of 1:1. If the ratios be considerably smaller or larger than the preferred, there result variations in the solubility of the modified drying oil in water and in the ease of the its precipitation upon the fibers of the slurry. We prefer to make the modified drying oil by heating 1 mol of the drying oil with 1 mol of the unsaturated acid at a temperature of approximately C. until the reaction is completed. Completion of the reaction is indicated by the disappearance of the two liquid phases and the formation of a uniformly clear liquid. The modified oil is then cooled and made soluble in water by adding ammonium hydroxide or other suitable alkali until the aqueous solution of the ammonium salt (or other salt) has a pH of about 8. The degree of alkalinity can be varied but for reason of economy, we prefer to go no higher than necessary since the greater the alkalinity, the more acid there will be required in order to precipitate the modified oil from solution. The modified oil can be made into such aqueous solutions so as to form concentrations of from 25-50% modified oil in water, While anhydrides are preferred in the Diels Alder condensation, the acids themselves can be used. Unsaturated dibasic acids frequently form anhydrides in the course of heating with the oil.

A general diagram of the means for preparing fibrous board in accordance with the invention follows:

Diels-Alder Condensate Oven As indicated before, various unsaturated carboxylic acids may be employed, among the dibasic acids that may be used are maleic, itaconic, fumaric, citraconic, pyrocinchonic, mesaconic, di and tetra hydrophthalic, acetylene dicarboxylic, dihydro naphthalene dicarboxylic, dihydro phenanthrene dicarboxylic acid, 3,4-dihydro-8,9- acephenanthrene-1,2-dicarboxylic acid and their anhydrides. Some monocarboxylic unsaturated acids also undergo the Diels Alder condensation and may be employed. These include acrylic, crotonic, sorbic, cinnamic, propiolic, tetrolic and dihydro naphthoic acids.

In the well known methods for manufacturing hardboard, the lignocellulosic fiber slurry is usually adjusted to approximate neutrality at which time the resin or other suitable binder is introduced to the slurry. Various binders may be used, for example, phenol-formaldehyde, or other soluble resins or various protein binders such as blood and casein. These binders are then precipitated on the fibers by acidifying the slurry to a pH generally within the range of 3-5 depending on the binder used.

In our preferred method for incorporation of the drying oil in a hardboard composition, we add an aqueous solution of the modified drying oil which has been rendered slightly alkaline with ammonium hydroxide to the fiber slurry after the precipitation of the binder. It is preferred that the modified oil be introduced after precipitation of thebinder; for the reason if there should be simultaneous precipitation of the binder and drying oil, the latter may inhibit to some extent the adhesion of the as binder to the fiber. The solubilized modified oil is vigorously agitated into the slurry and since the slurry has earlier been acidified to precipitate the binder, the modified oil leaves the water solution and becomes dispersed over the fibers. In an alternative procedure, the binder and solubilized oil may be precipitated together but as mentioned before, it is believed the modified oil in such a procedure interferes with the bonding of the binder to the fibers. Varying amounts of the modified drying oil may be added but it has been our experience that 310% of the modified drying oil based on the weight of the dry fiber gives a board of desirable characteristics for most uses.

Following the precipitation of the modified oil from the slurry, the fibrous mat is formed in the conventional manner, then subjected to a pressing operation at conventional temperatures and pressures, and next transferred to a heated oven which sets the oil to a resin-like material. The hardboard is held for 3-6 hours in the oven which is normally maintained at a temperature within the range of 300-400 F. If the temperature of the oven should be outside 300-400 F., the holding period or" the hardboard in the oven would be varied accordingly. The high chemical polarity of these modified oils increases adherence of the oil to the fibers of the wet mat, thus lessening the loss of the modified oil from the mat during the pressing operation. The incorporation of the modified tempering oil in the hardboard by introducing it to the slurry makes possible the uniform distribution of the oil throughout the wet mat. If an unmodified drying oil should be added to the fibrous slurry, there would be a substantial loss of the oil from the mat during the pressing operation in the form of an oil-water emulsion.

There are available several acid neutralizing materials for placing the Diels Alder condensation product into water solution. We have found ammonium hydroxide to be the most suitable of the commercial alkalies as it is easily handled. Various substituted ammonia compounds may be employed as well as soluble carbonates, hydroxides and oxides of the alkali metals such as soda ash and caustic soda.

If a case hardening effect is desired which would require that only the surface of the board receive maximum tempering the water soluble modified tempering oil may be sprayed on one or both surfaces of the wet felt mat prior to its placement in the hot press of the type commonly used in hardboard manufacture. Spraying may be done using a battery of spray nozzles across the Width of the mat as the mat leaves the felting equipment. In this embodiment of our invention, ammonium hydroxide is utilized for placing the Diels-Alder condensation product in aqueous solution since acidification need not be relied upon to precipitate the modified oil onto the fibers, but rather the precipitation may be brought about in the conventional hot pressing operation by decomposition of the water soluble ammonium salt through release of ammonia gas and liberation of the acidic modified oil from water solution. Following pressing the surface, tempered board is heated in an oven to polymerize the tempering oil.

In the manufacture of paper, the water soluble salt of the modified oil is added to the stock chest which contains the fibrous slurry. Faper stock is normally on the acid side and will precipitate the modified oil onto the fiber but if necessary, an acid may be added to the slurry to facilitate precipitation. The hot rolls through which the paper stock subsequently passes will bring about at least a partial setting up of the modified oil.

The following examples are set forth as illustrative of the present invention and are not to be construed as limiting thereto.

Example I The fibrous stock of this example contained approximately 59% rumen (the paunch contents of slaughtered cattle), 23% paper and 18% sawdust. Using a Bauer mill, each of these fibers was prepared separately. In the instance of the rumen, the mill was set with a clearance of .025 and at settings of .040" and 0.10" respectively for the paper and sawdust portions of the stock. The milled fibers were then mixed and concentrated for further use by separation of the solids over a screen. The screened material at this point had a solids content of 20% with the rest being water. The slurry was divided into three portions and each portion further diluted with water to obtain fibrous slurries having solid contents of 4%. The slurry of each portion had a pH of 6.5. Liquid whole blood to the extent of 5% of the dry fiber weight along with a precipitant of sodium ligno-sulfonate was added to each portion.

An aqueous solution of an ammoniated modified drying oil was prepared in the manner described above. The drying oil used in the preparation of Diels-Alder condensation product was linseed oil and the unsaturated acid utilized was the anhydride of itaconic acid. One mol of the drying oil was added to one mol of the itaconic acid. The pH of each slurry was adjusted to 4.3 through addition of sulfuric acid, thereby precipitating the blood binder upon the fibers of the slurry. The ammoniated drying oil was added to two of the portions of the slurry to the extent of 5% of the dry fiber weight. Each slurry was then transferred to a batch type felting box wherein the free water was drained off to form a mat of felted fibers. Each of the three mats Was then subjected to a cold pressing operation. The felts were then each individually placed in a conventional hot plate press at a temperature of 385 F. for 5 min. under 200 psi. The control board (which contained no modified drying oil) and one of the other boards were then transferred for 5 hours to an oven at a temperature within the range of 300-400 F.

The following table contains data to the modulus of rupture (p.s.i.), to the percent Weight increase, and to the percent thickness increase of each of the boards after immersion for 24 hours in water. The modulus of rupture information was gathered on the dry board.

The composite fibrous stock used in this example was prepared in the manner described above in Example I and was of the same formula. Here, the binder used was the water soluble resin phenol-formaldehyde which was added to the fibrous slurry in the amount of 3% based on the weight of the dry fiber. One mol of tung oil (890 parts) was mixed with 2 mols of maleic anhydride (196 parts) and heated to 160 C. until a clear, single phase liquid was obtained. This was suspended in three times its own weight of water and neutralized with ammonium hydroxide to a pH of 8. The aqueous solution of the ammonium salt of the modified drying oil was added to the slurry to the extent of 5% based on the weight of dry fiber weight. The subsequent processing was substantially in the manner described in Example I except that the baking operation was for 16 hours at C. Here again, there was a control to which no drying oil was added and only one of the boards which incorporated the modified oil was baked. The following table sets forth data relating to the three specimens. It will be noted that in addition to the substantial increase in strength, the use of the modified drying oil incorporated in a hardboard in accordance with our process lowers the sensitivity to moisture to about one-third of a board not treated with the modified oil.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In a process for incorporating a drying oil in a fibrous composition, the steps comprising introducing to the fiber in a water slurry an aqueous solution of a water soluble salt of a Diels Alder condensation product of a drying oil having conjugated double bonds and an un saturated carboxylic acid whose ethylenic function is conjugated with a carboxyl group, and precipitating the Diels- Alder condensation product on the fiber.

2. Ina process for introducing a drying oil to a fibrous composition, the steps comprising dispersing in a water slurry of the fiber a water soluble salt of a Diels-Alder condensation product, said condensation product being the reaction product of a drying oil having conjugated double bonds and an unsaturated carboxylic acid whose ethylene function is conjugated with a carboXyl group, precipitating the Diels-Alder condensation product upon the fiber of the slurry, forming a mat of fibrous material, and thereafter heating the mat to polymerize the Diels- Alder condensation product.

3. A process as described in claim 2 wherein the unsaturated carboxylic acid is selected from the group consisting of maleic acid, itaconic acid and their anhydrides.

4. A process for introducing a drying oil to a hard board composition which comprises dispersing in Water slurry of lignocellulosic fiber and binder a water soluble salt of a Diels-Alder condensation product of a drying oil having conjugated double bonds and an unsaturated carboxylic acid Whose ethylenic function is conjugated with the carboxyl group, adjusting the pH of the slurry to within the range of 3-5 to effect the precipitation of the Diels-Alder condensation product and of the binder from the slurry, forming a hardboard out of the fibrous material, and thereafter heating the board to set the Diels- Alder condensation product to a resin-like material.

5. An improved fibrous composition comprising a fibrous mat and a polycarboxylated modified drying oil uniformly dispersed throughout the mat, said polycarboxylated modified drying oil being a Diels-Alder condensation product of a drying oil having conjugated double bonds and an unsaturated carboxylic acid whose ethylenic function is conjugated with the carboxyl group.

6. A composition as described in claim 5 wherein the unsaturated carboxylic acid is maleic acid or its anhydride.

7. A composition as described in claim 5 wherein the unsaturated carboxylic acid is itaconic acid or its anhydride.

8. A process for introducing a drying oil to a paper stock which comprises introducing to a water slurry of the paper stock an aqueous solution of a Water-soluble salt of a Diels-Alder condensation product of a drying oil having conjugated double bonds and an unsaturated carboxylic acid whose ethylenic function is conjugated with the carboxyl group, and precipitating the Diels-Alder condensation product on the paper stock.

References Cited in the file of this patent UNITED STATES PATENTS 2,074,964 Larson Mar. 23, 1937 2,143,831 Ellis Jan. 10, 1939 2,298,914 Auer Oct. 13, 1942 2,306,281 Rust Dec. 22, 1942 2,637,650 Bradshaw May 5, 1953 2,683,089 Reynolds July 6, 1954 2,721,505 Mossberg Oct. 25, 1955 2,930,106. Wrotnowski Mar. 29, 1960 

1. IN A PROCESS FOR INCORPORATING A DRYING OIL IN A FIBROUS COMPOSITION, THE STEPS COMPRISING INTRODUCING TO THE FIBER IN A WATER SLURRY AN AQUEOUS SOLUTION OF A WATER SOLUBLE SALT OF A DIELS ALDER CONDENSATION PRODUCT OF A DRYING OIL HAVING CONJUGATED DOUBLE BONDS AND AN UNSATURATED CARBOXYLIC ACID WHOSE ETHYLENIC FUNCTION IS CONJUGATED WITH A CARBOXYL GROUP, AND PRECIPITATING THE DIELSALDER CONDENSATION PRODUCT ON THE FIBER. 